Cloudburst Summit is not the darkest place we observe from, but it is the darkest one we can reach after work on a Friday. The turnout sits at 7,018 feet on the Angeles Crest Highway, about an hour above La Cañada, with a clear horizon from the east round through south to the west. The Los Angeles basin lies to the south-west, and on an ordinary night its light dome reaches a third of the way to the zenith.
This new moon was not ordinary. A deep marine layer came ashore on Friday afternoon and stayed for the weekend, and from the summit we looked down on a flat grey floor of cloud with the city glowing faintly underneath it. The dome shrank to a low smear. The meter read 21.1 at the zenith on Saturday, the best figure we have recorded from this site in four autumns of keeping the log.
We had one list for the three nights: the autumn objects from the Messier catalogue, plus a second page of fainter targets to try if the sky allowed. It allowed most of them.
Conditions, night by night
Friday 11 September
Dark by 8:30, with the cloud deck already in place below. It was gusty from the north until about ten, which kept the seeing soft and held us to low power. Stars at 170× were swollen, and Saturn showed its rings as a thin ellipse but no detail on the globe. Transparency was the story. The Veil needed the filter only for its faintest filaments, and M31 ran past both edges of a two-degree field.
Saturday 12 September
The best night of the three, and one of the best we have had here. The wind dropped at dusk and the air steadied. From about eleven M33 was a naked-eye object with averted vision, which we manage from this site perhaps one night a year. We stayed until the zodiacal light came up in the east a little after four.
Sunday 13 September
Thin cirrus arrived from the west soon after dark and cost us half a magnitude. We kept to bright clusters, then spent the last clear forty minutes on M74 and packed up at midnight. Monday is still Monday.
The list
Forty-one objects went into the log over the weekend. These twelve are the ones worth writing up. The rest were the usual bright clusters, logged and enjoyed without comment.
| Object | Type | Night | What we saw |
|---|---|---|---|
| M31, M32, M110 Andromeda | Galaxy group | All three | Two dust lanes on Saturday, and NGC 206 as a soft patch |
| M33 Triangulum | Spiral galaxy | Sat | Naked eye with averted vision. NGC 604 a clear knot at 120× |
| M15 Pegasus | Globular cluster | Fri, Sat | Blazing core, with the halo resolved a third of the way across the field |
| M2 Aquarius | Globular cluster | Fri | Granular at 60×, resolved at 170× in the steadier moments |
| NGC 7293, Helix Aquarius | Planetary nebula | Sat | Broad grey ring through the filter, the centre plainly darker |
| NGC 253 Sculptor | Spiral galaxy | Sat | Long mottled streak filling half the field at 60× |
| NGC 6992, 6960, Veil Cygnus | Supernova remnant | Fri, Sat | Both arcs and Pickering's Triangle with the filter |
| M27 Vulpecula | Planetary nebula | Fri | The apple core filled out to a full oval |
| NGC 7331 Pegasus | Spiral galaxy | Sat | Bright core and one companion. Stephan's Quintet not seen |
| NGC 891 Andromeda | Edge-on spiral | Sat | A thin sliver. The dust lane suspected only |
| M74 Pisces | Spiral galaxy | Sun | Core, and a faint round haze after forty minutes |
| Double Cluster Perseus | Open clusters | All three | A naked-eye knot. The red stars in NGC 884 obvious in the binoculars |
Notes on a few of them
On Saturday M31 showed two dust lanes along its north-western side, the inner one sharp and the outer one only a change in tone. The star cloud NGC 206 was a soft brightening toward the south-western end. Both companions were plain at a glance: M110 large and even, M32 small and hard-edged, like a star out of focus.
The two southern objects are the ones the city normally takes from us. The Helix culminates 35 degrees up from here and NGC 253 only 30, both over the brightest part of the dome. With the basin under cloud the Helix was a broad grey ring through the filter, its centre clearly darker than the rim, and NGC 253 was a long mottled streak that filled half the field at 60×. Neither needed averted vision.
M15 is the sketch beside this entry. At 120× the core is a blaze that will not resolve whatever the seeing does, and the halo breaks into stars out to about a third of the field. The drawing took twenty-five minutes, which is about as long as a dim red light and cold fingers allow.
M74 has beaten us from this site twice. It is a face-on spiral with a small core and a great deal of very faint disc, and any sky glow at all removes the disc and leaves something that looks like a dim star. On Sunday, with cirrus coming, we found the core at once beside Eta Piscium and gave it forty minutes at 85× with a hood over the eyepiece. The haze around the core came and went, round and perhaps six arcminutes across at its best. No arms. We have logged it as seen and will try again from somewhere darker.
Stephan's Quintet did not show. NGC 7331 was bright and easy, with one of its small companions visible beside it, but the Quintet half a degree away was a suspicion at best, and a suspicion does not go in the log.
How the log is kept
Each object gets a line written at the eyepiece: time, magnification, filter, and a description made before looking anything up. Sketches are done in pencil on white paper, so stars are dark dots and nebulosity is shading, and they are inked at home the next day. The meter is read at the zenith on the hour. Seeing is judged on the Pickering scale from a star near the zenith at high power, and transparency on our own five-point scale, where 5 means the Milky Way shows structure down to the horizon.
If you go
The turnout holds about a dozen cars and has no facilities. Parking in the Angeles National Forest generally needs an Adventure Pass displayed on the dashboard. The highway is sometimes closed beyond Islip Saddle, and after storms it can be closed lower down, so check the road conditions before you leave. Bring more warm clothing than seems reasonable for September: it was 45 degrees with wind on Friday. Arrive before dark, park with your headlights pointing away from the telescopes, and use red light only.